Very simply:

"As ratified by the States and authenticated by Thomas Jefferson, Secretary of State:

A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed."

Security of a FREE state, AKA when the government decides to start patrolling my town and demand passes to go anywhere it is time to exercise that second amendment right. And if you think that day isn't approaching you have your head stuck in the sand.